The present invention relates to a tube, in particular to an artificial sausage casing, which is composed of mutually connected sections. At the connection point the sections end in linear cut edges, which extend approximately at right angles to the longitudinal axis of the tube. The cut edges of the sections extend parallel to one another. An adhesive tape extending around the outside of the tube connects the two sections and forms a leak-tight closure. The invention also relates to a process for the production of a tube having sections mutually connected in this way.
In the continuous production of tubes, it is frequently necessary to introduce coating liquids into the interior of the tube or to remove process gases which accumulate in the tube cavity. To accomplish this, the tube is provided at certain intervals with an aperture which is closed again by means of a masking after introduction of the coating liquid or removal of the process gases (German Offenlegungsschriften No. 1,814,590 and No. 2,934,306). It is also known, in order to open the tube, to incise a longitudinal slit and subsequently to cut out from the tube and discard the piece of tube provided with the incision. The ends of the two tube sections formed by the cutting-out of the piece of tube then have to be mutually connected again, which is generally done by pushing the end of one tube section a distance of about 10 cm into the cavity of the other tube section and fixing the connection by means of an adhesive strip placed around the tube.
The production of this overlapping connection between the two tube sections is possible only in a costly working step, which does not permit simple automation. This type of connection additionally has the severe disadvantage that, when pipe-shaped articles are introduced, for example, the shirring mandrel of a shirring apparatus in the production of tightly shirred sausage casings or the stuffing horn of a filling apparatus for forcing in pasty products, attention has to be paid to a particular direction of movement. The relative movement occurring between pipe and tube must always be such that the pipe, when passing the connection point, moves from the tube section positioned inside into the cavity of the other tube section. If by contrast the pipe is pushed through the tube in the reverse direction, it encounters the tube section positioned inside at the connection point, so that the process sequence is interrupted and the connection point may even be ruptured.
In the production of the tube, therefore, care must be taken to ensure that the tube sections which are situated inside at the connection points always form the downstream tube section, as seen in the machine direction, so that during shirring or filling, the tube running off the roll in the opposite direction is guided in the correct direction over the shirring mandrel or over the stuffing horn at each connection point. Consequently, if a tube roll is printed before further processing, the runoff direction of the printed, rewound tube is changed to the opposite direction. Because of the connection points, therefore, re-winding must take place in an additional working step after the end of the printing process.
A further connecting technique envisages adhesive butt jointing by means of adhesive strips. Even with the most accurate adhesive butt jointing, the winding tension, on the one hand, and shrinkage of the tube material on the roll, on the other hand, will result in the formation of a gap, which is masked by the adhesive strip. As a result, in the flattened state, the adhesive side of the adhesive strip of the top comes into contact with the adhesive side of the adhesive strip of the bottom, so that the tube is closed at the point of adhesion and cannot be opened easily or without damage.